Gaining a sense of perspective

We’re publishing the shortlisted entries to the 2012 Wellcome Trust Science Writing Prize. In this piece, Susannah Lydon takes us with her on a scientific pilgrimage to find fearsome fossils and a sense of our place in the story of life.

The Burgess Shale (Credit: Susannah Lydon)

A few years ago, I made a pilgrimage. I travelled thousands of miles. I endured the final few miles of my journey on foot. And when I reached the site, I experienced a profound feeling of awe, which has stayed with me ever since. Visiting a scientific shrine can be a powerful experience.

The Burgess Shale is a rock formation in the Canadian Rockies, near a town called Field in British Columbia. A little over 500 million years old, these rocks contain fossils which have become world-famous because of their exceptional preservation and what they tell us about the early history of life on Earth. The fossil record as a whole is a highly biased sample, since the natural processes of decay, destruction and rock-recycling obliterate most evidence of living things, particularly the squishy bits. But the fossils of the Burgess Shale show soft part preservation, and represent a whole range of marine creatures that would never normally make it into the fossil record: an extraordinary triumph against the odds.

What makes the Burgess Shale so iconic? Part of the immediate appeal of the fossils is their weirdness. Not just one peculiar beast, but a whole bucketful of oddities with too many eyes, too many spikes and claws, or isolated limbs mistaken for entire animals. Trilobites, those worthy and reliable inhabitants of ancient seas, are present, but the rest of the animals are more like a Cambrian Addams Family than your typical fossil assemblage.

Many of them are (like trilobites) types of arthropod – the group represented today by insects, crustaceans, spiders and centipedes. Back in the mid-Cambrian, the top predator was Anomalocaris. At a then enormous 50 cm long, Anomalocaris was a killing machine with large bulging eyes, two grasping claws, a body and tail made of lobes for swimming, and a mouth resembling, oddly, a pineapple ring. Opabinia, another lobed swimmer, had a single huge, clawed appendage and five (yes, five!) stalked eyes on its head. Hallucigenia was originally reconstructed as a bizarre, stilt-walking scavenger with a single row of tentacles down its back. It has since been flipped over and rehabilitated, and currently resides within a group still found today: the onychophorans, or ‘velvet worms’.

Beyond the arthropods, Wiwaxia resembles a marine, armoured mini-hedgehog. Pikaia, a 5 cm long, eel-like creature with a pair of deely-bopper tentacles, is thought to be a primitive member of our very own group which developed backbones.

The bewildering diversity we see in the Burgess Shale is part of the evidence we have for the Cambrian Explosion: the idea that, about 500 million years ago, there was a step-change in the evolution of multicellular life and an explosion of new forms appeared, many representing the groups we see today. The Burgess Shale is not unique: similarly preserved fossils of around the same age have been discovered all over the world and have provided more evidence. While the Burgess Shale may appear weird to us, it appears to have been fairly normal for a shallow sea in the mid-Cambrian.

I first learnt about the Burgess Shale as an undergraduate – and I was hooked. I learnt that the same fossils could be interpreted in wildly different ways but that, since their discovery about a century ago, each generation of scientists built on and refined the ideas of the last. I learnt that the same bunch of fossils could be used to argue very different viewpoints in evolutionary theory. Eventually I taught classes about the Burgess Shale, and I saw some students get the same gleam in their eye when they comprehended just how extraordinary, and how improbable, this window into the past was. And when I got an opportunity to visit the very quarry where Charles Walcott first uncovered these wonders – now a restricted World Heritage Site within the Rocky Mountain World Heritage Parks – ‘pilgrimage’ really was the best word to describe my feelings as we hiked up into the mountains and eventually emerged above the tree line to that site.

Some science has no economic benefit. It does not cure disease, combat climate change or accelerate technological progress. What it does is tell us how we fit into the story of life, the story of the universe. The tangible sense of connection I felt with a lost world, half a billion years ago, informs my world view. Human beings are such a small part of the bigger picture and we would do well to be reminded of that from time to time. All science which deals with vast scales, whether palaeontology or astrophysics, provides this illuminating perspective, and that is why it is important.

Susannah Lydon

Susannah Lydon

This is an edited version of Susannah’s entry in the professional scientist category. Views expressed are the author’s own.

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